The production of gases from coal is receiving renewed attention in the present environment of high energy prices. Of particular interest is the catalytically enhanced gasification of coal with steam in a fluidized bed reactor. Such processes have the potential of being energy efficient and requiring lower investment costs.
The gasification of coal is typically achieved by reacting steam and coal at a very high temperature, or at moderate temperatures in the presence of alkali metal catalysts. Early work focused on the use of Group I and II metals loaded on coal particles as catalysts. However, these processes experienced shortcomings in catalyst-loading on coal and catalyst recovery and recycle from the gasifier discharged char. U.S. Pat. No. 3,828,474 describes the production of methane from hydrocarbons using a catalyst such as supported nickel catalyst promoted with alkali metal. U.S. Pat. No. 3,958,957 discloses a method of producing methane from coal using potassium as a gasification catalyst. U.S. Pat. No. 4,092,125 discloses a hydrothermal method for incorporating catalyst on coal. U.S. Pat. No. 3,998,607 and U.S. Pat. No. 4,057,512 disclose methods of alkali metal recovery. U.S. Pat. No. 4,094,650 discloses producing methane and carbon dioxide from carbonaceous feed material in the presence of a carbon-alkali metal catalyst and added hydrogen and carbon monoxide. U.S. Pat. No. 4,204,843 discloses a method wherein both alkali metal and alkaline earth metal catalysts are used. U.S. Pat. No. 4,468,231 discloses a method wherein alkali metal and alkaline earth metal cations are ion-exchanged in the presence of an oxidizing gas. GB 1599932 discloses a loading method that employs air oxidation of coal to increase oxygen content and treats coal with alkaline solution of hydroxides of potassium or sodium or alkaline earth metals.
While it has been suggested to improve the gasification of coal by admixing coal with a selected catalyst, or catalysts, techniques heretofore suggested have not been entirely successful. For example, known methods of impregnating coal with catalyst include: a) physical admixing of catalyst with coal, and b) incipient wetness (“IW”) impregnation, wherein a catalyst-containing solution is added to a dry coal, and the volume of the solution is not in excess, but is instead just enough to completely fill the pores of the coal. These methods of coal impregnation suffer the drawback of producing a coal with catalyst loading that is not highly dispersed, and thus a coal with reduced gasification efficiency. The art has placed little emphasis on catalyst-loaded coal with highly dispersed catalyst loading, and processes to prepare same. Accordingly, it is an object of the present invention to provide improved processes for the production of methane from coal. It is also an object of the present invention to provide improved processes for loading catalyst onto coal so as to provide coal compositions particularly adapted for the gasification of coal to methane.